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Hey again,<br>
<br>
I can almost taste success. I imagine it being sweet, like sugar.
Entirely unlike the bitter lemony sourness of 'not quite there' I
have in my mouth now. Help me see the error of my ways!<br>
<br>
Inspired by the code Matthew sent my way, I've cobbled together the
following object in C++ that is supposed to create a pipeline, share
the current OpenGL context with it, grab samples arriving at the
appsink and provide the texture ID's to the main thread for usage.<br>
<br>
videoTester.h<br>
<a class="moz-txt-link-freetext" href="http://hastebin.com/sutoyuxoci.coffee">http://hastebin.com/sutoyuxoci.coffee</a><br>
<br>
videoTester.cpp<br>
<a class="moz-txt-link-freetext" href="http://hastebin.com/gohofababi.cpp">http://hastebin.com/gohofababi.cpp</a><br>
<br>
In the main application, the following happens:<br>
<br>
Cinder sets up all the win32 app stuff, including an OpenGL context.<br>
VideoTester4 is instantiated with paths pointing to a webm video and
a passthrough fragment shader (no parameters).<br>
prepPipeline() is called.<br>
launchPipeline() is called.<br>
The generated Texture ID is inspected via imdebug (an awesome
texture debugging tool) via this call:<br>
imdebugTexImage( GL_TEXTURE_2D, mVidTester4->getTexId(), GL_RGBA
);<br>
<br>
Note that I intentionally do *not* unref any of the associated
frame/sample/buffer objects, just to keep things simple. However,
all I seem to get when I use imdebug to inspect the textures, are
empty 0,0 sized textures that (not surprisingly) contain nothing at
all. I wondered if GL_TEXTURE_2D might be the wrong texture target
and have also tried GL_TEXTURE_RECTANGLE without any luck. Is there
any place I can read the texture target from?<br>
<br>
Anyway, the pipeline does not report any errors along the way, and
the gstreamer log only contains a few (harmless?) warnings:<br>
<br>
0:00:00.683792474 1836 0CFBEE60 WARN gldisplay
gstgldisplay.c:169:gst_gl_display_new: Could not create display.
user specified (NULL) (platform: (NULL)), creating dummy<br>
0:00:00.686256033 1836 0CFBEE60 WARN basesrc
gstbasesrc.c:3470:gst_base_src_start_complete:<source> pad not
activated yet<br>
0:00:00.686752850 1836 0CFBEE60 WARN basesrc
gstbasesrc.c:3470:gst_base_src_start_complete:<source> pad not
activated yet<br>
<br>
The texture ID increases as the program continues execution (which
is to be expected), and inspecting the Textures in the actual
callback thread with imdebug crashes the program. This has to be due
to the fact that the callback function executes in a separate thread
as Matthew told me last we spoke.<br>
<br>
I've poked a bit around with the various Gst objects without any
luck so far. Any ideas/clues as to what I'm missing or how to narrow
down what the problem might be?<br>
<br>
Regards,<br>
Lasse<br>
<br>
<div class="moz-cite-prefix">On 16-01-2015 22:21, Matthew Waters
wrote:<br>
</div>
<blockquote cite="mid:54B98EEE.1020106@gmail.com" type="cite">
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<br>
<div class="moz-cite-prefix">On 17/01/15 06:42, Lasse Laursen
wrote:<br>
</div>
<blockquote cite="mid:%3C54B96992.1030209@lasselaursen.com%3E"
type="cite">
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http-equiv="Content-Type">
Hey Matthew,<br>
<br>
Thanks for the reply and especially the example. I'm working on
getting it function with the cinder framework. At first it
seemed quite odd to hand over the context as a result of a bus
message, but I can see the logic in not needing to create a
secondary OpenGL context for gstreamer to make textures in, if
one already exists. I do have one question though:<br>
<br>
Is it vital to turn off the OpenGL context when sharing it with
Gstreamer? I've done a little context sharing before and I don't
recall having to actively turn any contexts 'off'.<br>
</blockquote>
<br>
No it is not required to turn off the context.<br>
<br>
<blockquote cite="mid:%3C54B96992.1030209@lasselaursen.com%3E"
type="cite"> Regards,<br>
Lasse<br>
<br>
<div class="moz-cite-prefix">On 16-01-2015 00:27, Matthew Waters
wrote:<br>
</div>
<blockquote cite="mid:54B85AE6.6000607@gmail.com" type="cite">
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http-equiv="Content-Type">
A couple of points added inline.<br>
<br>
<div class="moz-cite-prefix">On 16/01/15 03:14, Lasse Laursen
wrote:<br>
</div>
<blockquote cite="mid:%3C54B7E76D.6000904@lasselaursen.com%3E"
type="cite">
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charset=utf-8">
Hello!<br>
<br>
Apologies for the double post, but my inept handling of
Thunderbird caused my last post to be appended to an
unrelated thread. Sorry about that Luis dArquer.<br>
<br>
For the sake of posterity, here's is the original question:<br>
<br>
I feel like I am so close to finally getting through to the
other side with this problem, so I'm hoping someone can give
me a few clues as to what pieces of the puzzle are missing.
I used to use gStreamer as a pure 'decoding' library using
this simple pipeline: <br>
<br>
uridecodebin uri=" + mPathToVideoFile + " ! videoconvert
! appsink name=sink
caps="video/x-raw,format=RGB,pixel-aspect-ratio=1/1"; <br>
<br>
With this pipeline, I could quite easily grab the frames
arriving at the sink and use them however I pleased. Mostly
just throwing them on a texture in OpenGL and displaying
them various places. This approach is - of course - quite
horrible. I'm not making use of gstreamer as a fully-fledged
media pipeline. So to rectify that - and because I'd like to
run some simple shaders on the video data - I am now using
this (almost as) simple pipeline: <br>
<br>
uridecodebin uri=" + mPathToVideoFile + " ! glshader
name=shader location=" + pathToShader + " vars=\"float
silver = float( 0.8 ); \" ! appsink name=sink
caps=\"video/x-raw,format=RGB,pixel-aspect-ratio=1/1\""; <br>
</blockquote>
<br>
1. You should set the appsink caps to contain the
memory:GstGLMemory caps features. e.g.
video/x-raw(memory:GstGLMemory),format=RGBA... see
gst-inspect-1.0 glshader for the supported formats and
features. Otherwise, glshader (and any GL element) will
download the texture upon seeing the system memory caps.<br>
<br>
<blockquote cite="mid:%3C54B7E76D.6000904@lasselaursen.com%3E"
type="cite"> I make sure to share my current OpenGL context
with the glshader element thusly: <br>
<br>
mPipeline_ShaderPre = gst_bin_get_by_name( GST_BIN(
mGstPipeline ), "shader" ); <br>
HGLRC mainContext = ::wglGetCurrentContext(); <br>
g_object_set( mPipeline_ShaderPre, "other-context",
mainContext, NULL ); <br>
</blockquote>
<br>
2. The "other-context" property expects a GstGLContext rather
than a platform specific handle. You can wrap a context
handle using gst_gl_context_new_wrapped(). However, in master
there is no "other-context" property anymore so the sharing of
GL context happens using GstContext. See for example <a
moz-do-not-send="true"
href="http://cgit.freedesktop.org/gstreamer/gst-plugins-bad/tree/tests/examples/gl/sdl/sdlshare.c#n232">http://cgit.freedesktop.org/gstreamer/gst-plugins-bad/tree/tests/examples/gl/sdl/sdlshare.c#n232</a>
and the GstContext documentation.<br>
<br>
<blockquote cite="mid:%3C54B7E76D.6000904@lasselaursen.com%3E"
type="cite"> Not sure if this is correct to be honest, but I
didn't see any errors in gstreamers logs. Anyway - fast
forward to my callback function that fires whenever a sample
is ready at the sink I proceed to grab a Sample, from which
I grab a Buffer, from which I grab a Frame, from which I
grab a Texture ID, thusly: <br>
<br>
GstSample* gstVideoSinkSample = gst_app_sink_pull_sample(
GST_APP_SINK( appsink ) ); <br>
GstBuffer* gstBuffer = gst_sample_get_buffer(
gstVideoSinkSample ); <br>
if ( !gst_video_frame_map( &gstFrame, &gstInfo,
gstBuffer, static_cast<GstMapFlags>( GST_MAP_READ | (
GST_MAP_FLAG_LAST << 1 ) ) ) ) <br>
{ <br>
errorToConsole( true, "Failed to map video frame" );
<br>
} <br>
GLuint textureId = *(guint *) gstFrame.data[0]; <br>
<br>
The result is the number 6. Which I felt was a plausible
Texture ID handle. But when I then use a lovely tool named
imdebug, and presume that the target for the texture is
GL_TEXTURE_2D (which might be wrong), it throws a fit,
because it attempts to determine the width and height of
said texture via these calls: <br>
<br>
glBindTexture(target, texture); <br>
glGetTexLevelParameteriv(target, 0, GL_TEXTURE_WIDTH,
&w); <br>
glGetTexLevelParameteriv(target, 0, GL_TEXTURE_HEIGHT,
&h); <br>
<br>
So clearly something is wrong. Some place along this winding
road, I've misunderstood something or overlooked something.
I'd much appreciate any suggestions/clues! <br>
<br>
I myself am wondering if a callback at the sink is the right
place to grab the texture ID, but I'm not sure how to get at
it any earlier, and if that's wise. I am also unsure of how
long this texture Id is valid if I want to render it on to a
quad. I hope someone can shed a bit of light! <br>
</blockquote>
<br>
It will be valid for as long as it's not overwritten/reused by
the producing element which generally means while you keep a
ref to the buffer or have the video frame mapped.<br>
<br>
<blockquote cite="mid:%3C54B7E76D.6000904@lasselaursen.com%3E"
type="cite"> Regards, <br>
Lasse <br>
<br>
<div class="moz-signature">-- <br>
Lasse Farnung Laursen<br>
Researcher at the University of Tokyo<br>
<a moz-do-not-send="true"
href="http://www.lasselaursen.com">www.lasselaursen.com</a><br>
Twitter: <a moz-do-not-send="true"
href="https://twitter.com/PMP_J">@PMP_J</a></div>
</blockquote>
<br>
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<br>
<div class="moz-signature">-- <br>
Lasse Farnung Laursen<br>
Researcher at the University of Tokyo<br>
<a moz-do-not-send="true" href="http://www.lasselaursen.com">www.lasselaursen.com</a><br>
Twitter: <a moz-do-not-send="true"
href="https://twitter.com/PMP_J">@PMP_J</a></div>
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</blockquote>
<br>
<div class="moz-signature">-- <br>
Lasse Farnung Laursen<br>
Researcher at the University of Tokyo<br>
<a href="http://www.lasselaursen.com">www.lasselaursen.com</a><br>
Twitter: <a href="https://twitter.com/PMP_J">@PMP_J</a></div>
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